System knowledge for maritime

Diesel particulate filter

Diesel particulate filters (DPF) consist of a ceramic structure of small channels that are alternately blocked, forcing exhaust gases to flow through the thin porous walls of the filter block. Diesel particles or soot get trapped in the porous walls of the diesel particle filters. If the temperature is high enough the soot will oxidize (burn) in a process called regeneration. After oxidation a small amount of ash remains on the filter wall. The majority of the ash comes from the lubricant oil, the rest from fuel and engine wear.   

Xeamos applies robust silicon carbide diesel particle filters with a proven long-term reliability in marine applications. Our particle filters reduce more than 97% of the particulate mass (PM) emissions from the engine.

Catalytic coatings

The average exhaust temperature in most marine engine applications is too low to complete the regeneration of the DPF. For this reason a catalytic coating is applied on the porous walls of the DPF. There are different types of catalytic coatings containing base metals and/or precious metals. Catalytic coatings lower the regeneration temperature of the trapped soot and enhance the oxidation of the hydrocarbons present in the exhaust gases. Hydrocarbons are unburned fuel molecules that can be noticed as diesel smell and fatty deposits on the water in combination with wet exhaust systems. The type of coating is selected based on the maximum sulphur content of the fuel, engine load profile and the required reduction of hydrocarbons. The correct selection of DPF type and catalytic coatings requires knowledge of experts. Our engineers are trained to provide the best technical solution, made to measure for your specific needs.

Passive versus active regeneration

The average exhaust temperature in most marine engine applications is too low to complete the regeneration of the DPF under all circumstances, even if catalytic coatings are applied on the porous walls of the DPF During normal loading of the engine, temperatures can be high enough to allow for passive regeneration. However after a prolonged period of low load operation the temperature of the exhaust gases has to be increased periodically to limit the pressure increase due to the soot build up in de DPF. . Xeamos applies diesel fuel burners or electric heaters that have been developed in-house.

Bypass valve

All Xeamos DPF systems are equipped with an automatic bypass valve, a safety device that limits back pressure in the exhaust system in the event of a system malfunction. Malfunctions can be caused by a failure of the active regeneration or by engine issues such as a faulty fuel injector or turbo. In case the bypass valves opens, an alarm is raised by the system controller to request for further investigation about the root cause of the intervention. The availability of the engine is ensured and the DPF system remains operational, with a limitation of soot reduction as a result.

Controls

The control of a diesel particle filter system with active regeneration is rather complex. The system is controlled and monitored by a state-of-the-art PLC-based control system with ParticulateControl Diagnostics (PCD). This means that the system is tamper-proof, meeting the requirements of the applicable legislation. Xeamos control systems are Class-approved and ensure a reliable and safe operation. The controller allows for easy communication or integration with the ship’s AMS through a MOD bus protocol or analogue I/O. Xeamos systems offer remote monitoring to provide support to chief engineers when required. All system values and signals as well as events, warnings and alarms are recorded and stored in a non-erasable log file. All logged data can be easily uploaded through a remote connection for further analysis and reporting by Xeamos engineers.

Reactor housing design

The reactor housing for our SCR and/or DPF systems is designed for the specified operating conditions. The pressure drop, flow uniformity and temperature distribution are accurately simulated using advanced CFD software. Mechanical stress calculations are made with our FEM software tools using worst-case scenarios of maximum exhaust temperatures and pressures. The effect of low-cycle fatigue on the steel has to be taken into account to prevent premature failure of the system, especially with wet underwater exhausts. Different (stainless) steel types can be applied depending on the application and customer requirements.

Relevant products

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